The present invention concerns design of filters for electrical circuits and pertains particularly to a notch filter implemented using analog sampling.
A filter rejects some frequencies within a signal and allows other frequencies to be transmitted. In a low-pass filter the frequencies that are transmitted extend from zero to some maximum frequency. In a high-pass filter the frequencies that are transmitted are greater than some minimum frequency. In a band-pass filter, the frequencies that are transmitted are between a minimum frequency and a maximum frequency. In a notch filter, a very narrow range of frequencies is removed from the signal.
There are many ways to construct filters. Generally, when designing filters it is desirable to very particularly pass only desired frequencies while as completely as possible rejecting other frequencies. Generally, filters that are very effective at passing desired frequencies and rejecting other frequencies are difficult to design and expensive to build. The present invention sets out filters that are elegant in design, inexpensive to build and extremely effective.